A vehicular sensor such as an acceleration sensor, a pressure sensor and an exhaust gas sensor outputs an electric signal, which varies with a physical quantity of a detection object. Such a sensor may be a voltage output type, a capacitance detection type, a current output type or the like. An A/D converter mounted in a vehicular microcomputer converts an input analog voltage into a digital data.
In case that the sensor produces an output signal, which is not an analog voltage, signal processing circuits are provided at a pre-stage of the A/D converter for signal processing (for example, patent document 1). The signal processing circuits are, for example, a special circuit having a C/V conversion function or an I/V conversion function and an amplifier circuit for amplifying an output signal of the special circuit. Alternatively, an A/D converter having an amplification function is employed (for example, patent document 2).    Patent document 1: JP 2008-216135A    Patent document 2: JP 2008-104142A (US 2008/0074304 A1)
In case that a C/V converter, an amplifier and the like are provided in addition to an A/D converter as disclosed in patent document 1, circuit area and power consumption increase correspondingly. In case that an A/D converter having an amplification function is provided as disclosed in patent document 2, no amplifier need be provided separately. However, a C/V converter need be provided. Circuit area and power consumption increase correspondingly.